Mobile wireless communications device including parallel nfc loop antennas and associated methods

ABSTRACT

A mobile wireless communications device includes a portable housing, an NFC transceiver carried by the portable housing, and an antenna assembly coupled to the NFC transceiver and comprising a plurality of loop antennas connected in parallel, and progressively increasing in size from an innermost loop antenna to an outermost loop antenna.

TECHNICAL FIELD

This application relates to the field of communications, and moreparticularly, to wireless communications systems and related methods.

BACKGROUND

Mobile communication systems continue to grow in popularity and havebecome an integral part of both personal and business communications.Various mobile devices now incorporate Personal Digital Assistant (PDA)features such as calendars, address books, task lists, calculators, memoand writing programs, media players, games, etc. These multi-functiondevices usually allow electronic mail (email) messages to be sent andreceived wirelessly, as well as access the internet via a cellularnetwork and/or a wireless local area network (WLAN), for example.

Some mobile devices incorporate contactless card technology and/or nearfield communication (NFC) chips. NFC technology is commonly used forcontactless short-range communications based on radio frequencyidentification (RFID) standards, using magnetic field induction toenable communication between electronic devices, including mobilewireless communications devices. This short-range high frequencywireless communications technology exchanges data between devices over ashort distance, such as only a few centimeters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a wireless mobile communicationssystem in accordance with an example embodiment.

FIG. 2 is a schematic diagram of the antenna assembly illustrated inFIG. 1.

FIG. 3 is a schematic block diagram illustrating example mobile wirelesscommunications device components that may be used with the system anddevices of FIGS. 1 and 2.

DETAILED DESCRIPTION

The present description is made with reference to the accompanyingdrawings, in which various embodiments are shown. However, manydifferent embodiments may be used, and thus the description should notbe construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete. Like numbers refer to like elements throughout.

In accordance with one exemplary aspect, a mobile wirelesscommunications device comprises a portable housing, an NFC transceivercarried by the portable housing, and an antenna assembly carried by theportable housing and coupled to the NFC transceiver. The antennaassembly may comprise a plurality of nested loop antennas coupled inparallel, and progressively increasing in size from an innermost loopantenna to an outermost loop antenna.

As will be explained in greater detail below, the antenna assemblymaintains payment certification requirements (as defined by EMVCo) forlarge tags, while also increasing performance for small tags. Small tagsmay be used for Bluetooth pairing and interfacing with docking stations,for example. The plurality of nested loop antennas may benon-concentric. This further helps to increase magnetic flux coveragefor the small tags.

The plurality of nested loop antennas may comprise three loop antennas.Each loop antenna may have a rectangular shape with opposing ends andopposing sides coupled thereto.

The mobile wireless communications device may further comprise a pair ofantenna feed points, and wherein the plurality of nested loop antennaseach have respective ends adjacent one another, and adjacent the pair ofantenna feed points and coupled thereto. The antenna assembly mayfurther comprise a dielectric substrate, and wherein each loop antennamay comprise at least one loop conductor carried by the dielectricsubstrate.

The portable housing may comprise a removable battery cover, and whereinthe antenna assembly may be carried by the removable battery cover. Theinnermost loop antenna may be about 15 mm by 15 mm, and the outermostloop antenna may be about 85 mm by 54 mm.

The mobile wireless communications device may further comprise acellular transceiver carried by the portable housing, and a cellularantenna coupled to the cellular transceiver.

A method aspect is directed to making a mobile wireless communicationsas described above. The method may comprise positioning an NFCtransceiver within a portable housing, and coupling an antenna assemblyto the NFC transceiver within the portable housing. The antenna assemblymay comprise a plurality of nested loop antennas connected in parallel,and progressively increasing in size from an innermost loop antenna toan outermost loop antenna.

Referring initially to FIG. 1, the mobile wireless communications device10 includes a portable housing 12 and an NFC transceiver 20 carried bythe portable housing, and an antenna assembly 30 coupled to the NFCtransceiver. The antenna assembly 30 includes a plurality of loopantennas connected in parallel, as will be discussed in greater detailbelow. The NFC transceiver 20 may communicate with an NFC terminal 40,and may operate in either a device reader mode and a device cardemulation mode.

The mobile wireless communications device 10 also includes wirelesstransceiver circuitry 50 carried by the portable housing 12, and anantenna 52 coupled to the wireless transceiver circuitry 50. Thewireless transceiver circuitry 50 may be cellular transceiver circuitryor other types of wireless communications circuitry, and may communicateany combination of voice and data, such as email, via a wireless network14.

Example mobile wireless communications devices 10 include portable orpersonal media players, such as music or MP3 players, and video players.Mobile wireless communications devices 10 may also include portablegaming devices, portable or mobile telephones, smartphones, tabletcomputers, and digital cameras, for example.

The mobile wireless communications device 10 includes a display 54carried by a front exterior surface of the portable housing 12. Thedisplay 54 may be a liquid crystal display (LCD) and may be configuredto display information relating to a data or voice communications.

A processor 56 is carried the portable housing 12 and is coupled to thewireless transceiver circuitry 50, the NFC transceiver 20 and thedisplay 54. The processor 56 may be implemented using hardware andsoftware components for causing the mobile wireless communicationsdevice 10 to perform the various functions or operations describedherein.

The mobile wireless communications device 10 also includes a powersource 58. For example, the power source 58 may be a rechargeablebattery. Nonetheless, other types of power sources may be used.

The mobile wireless communications device 10 is particularlyadvantageous with respect to NFC communications, as will now bediscussed in greater detail. The antenna assembly 30 maintains paymentcertification requirements (as defined by EMVCo) for large tags, whilealso increasing performance for small tags.

By way of background, NFC is a short-range wireless communicationstechnology in which NFC-enabled devices are “swiped,” “bumped” orotherwise moved in close proximity to communicate. NFC enables exchangeof data between two or more wireless devices, generally by inductivecoupling. Inductive coupling may be used for completing payment cardtransactions, for interfacing with smart posters, for Bluetooth pairingand interfacing with docking stations, for example. Payment cardsinclude credit cards, gift cards and bank cards, for example.

Inductive coupling refers to the generation of voltage/current in oneloop or coil due to (and proportional to) a change in voltage/current(and hence the corresponding magnetic field) in another loop or coil.The two loops are termed as being “inductively coupled” to each other,and which may thus be viewed as antennas. Currently, NFC communicationsis standardized and designed to operate within the globally availableand unlicensed radio frequency ISM band of 13.56 MHz.

The antenna assembly 30 includes a plurality of nested loop antennas 32,34, 36 connected in parallel, as best illustrated in FIG. 2. Althoughthree loop antennas 32, 34, 36 are connected in parallel, the actualnumber may be more or less depending on the intended applications or theamount of space available within the mobile wireless communicationsdevice 10.

The selected number of loop antennas to be connected in parallel stillneeds to support a quality (Q) factor of less than 35, as readilyappreciated by those skilled in the art. The Q factor is determined bydividing the inductive reactance (ohms) by the resistive losses in theloops (ohms) at the operating frequency.

The loop antennas 32, 34, 36 that are connected in parallelprogressively increase in size from an innermost loop antenna 32 to anoutermost loop antenna 36. The loop antennas 32, 34, 36 are connected tofeed points 60, 62 that are coupled to the NFC transceiver 20. The loopantennas 32, 34, 36 each have respective ends adjacent one another, andadjacent the pair of antenna feed points 60, 62.

In addition, the loop antennas 32, 34, 36 are non-concentric, and have arectangular shape with opposing ends and opposing sides coupled thereto.The antenna assembly 30 may include a dielectric substrate 66, with eachloop antenna 32, 34, 36 comprising at least one loop conductor carriedby the dielectric substrate.

As discussed above, the mobile wireless communications device 10includes a power source 58 that may be configured as a rechargeablebattery carried by a back exterior surface of the portable housing 12.The rechargeable battery 58 is removable from the portable housing 12.For this particular configuration of a mobile wireless communicationsdevice 10, the portable housing 12 comprises a removable battery cover15, and wherein the antenna assembly 30 is carried by the removablebattery cover, as illustrated in FIG. 2.

Performance of the antenna assembly 30 will now be discussed inreference to TABLE 1. Antenna performance will be compared against asingle antenna. Performance of the single antenna and the antennaassembly 30 are directed towards 4 different tag sizes that conform toindustry standards.

The smallest tag size is 15×15 mm, the middle tag sizes are circularshaped and have a diameter of 30

TABLE 1 Single Loop Antenna Triple Loop Antenna (Max ‘Z’ Distance) (Max‘Z’ Distance DEVICE READER MODE PERFORMANCE Tag Size 15 × 15 mm 15 mm 21mm 30 mm dia. 24.5 mm   28.5 mm   38 mm dia. 27 mm 30 mm 85 × 54 mm 35mm 36 mm DEVICE CARD EMULATION MODE PERFOMANCE Modulation Type A 53.5mm   55 mm B 51 mm 52.5 mm  mm and 38 mm, respectively. The largest tag size is 85×54 mm.

The smallest tag size may be used for Bluetooth pairing and interfacingwith docking stations, for example. The circular shaped tags may be usedto receive web site information, for example, from smart posters.

The largest tag size meets EMVCo contactless specifications for paymentsystems. EMVCo, owned by American Express, JCB, MasterCard and Visa,ensures global interoperability of chip-based payment cards withacceptance devices, including point of sale terminals and ATMs.

Operation of the NFC transceiver 20 in a device reader mode will bediscussed first. The max “z” distance for each antenna configurationcorresponds to a height or separation distance from the NFC terminal 40.For the smallest tag size, the single antenna has a separation distanceof 15 mm, and the antenna assembly 30 has a separation distance of 21mm. For the circular shaped tag having the 30 mm diameter, the singleantenna has a separation distance of 24.5 mm, and the antenna assembly30 has a separation distance of 28.5 mm. For the circular shaped taghaving the 38 mm diameter, the single antenna has a separation distanceof 27 mm, and the antenna assembly 30 has a separation distance of 30mm. For the largest tag size, the single antenna has a separationdistance of 35 mm, and the antenna assembly 30 has a separation distanceof 36 mm.

The increased separation distances provided by the antenna assembly 30flattens out as antenna sizes increase. However, the antenna assembly 30advantageously increases small tag reading distances. The loop antennas32, 34, 36 in the antenna assembly 30 are coupled to antenna feed points60 and 62, which provide a voltage generated by the NFC transceiver 20.The voltage provided by the feed points 60, 62 generate current thattravels around each loop antenna 32, 34, 36 to generate magnetic fields.The magnetic fields are at a constant level and are evenly distributedin the loop areas, i.e., x and y.

The loop antennas 32, 34, 36 pick up magnetic fields within their loopareas. Since the small loop antenna 32 is about ⅕ the size of the largeloop antenna 36, it only picks up about ⅕ of the magnetic field ascompared to that of the larger loop antenna 36. Similar analysis appliesto the middle loop antenna 34.

Since the loop antennas 32, 34, 36 are nested and non-concentric, andthe smaller size loop antennas 32, 34 are positioned within the largersize loop antenna 36 toward the top of the mobile wirelesscommunications device 10, the field patterns are directed toward thetop. The inductive coupling from the larger loop antenna 36 helps toincrease the inductive coupling of the middle loop antenna 34, and theinductive coupling from the middle and larger loop antennas 36, 34 helpto increase the inductive coupling of the small loop antenna 32.

Operation of the NFC transceiver 20 in a device card emulation mode willbe now discussed. The max “z” distance for each antenna configurationcorresponds to a height or separation distance from the NFC terminal 40.Based on ISO standards, there is a modulation type A and a modulationtype B. For the single antenna, the separation distances correspond to53.5 mm and 51 mm, respectively. For the antenna assembly 30, theseparation distances correspond to 55 mm and 52.5 mm, respectively.There is a slight increase in performance with the antenna assembly 30.

As noted above, antenna assembly 30 needs to support a quality (Q)factor of less than 35. Another definition of the Q factor correspondsto bandwidth. The wider the bandwidth the lower the Q factor. With asingle antenna configuration, resistances are typically added to dropthe Q factor to meet the data rate requirement. In lieu of addingresistances, additional loop antennas can be connected in parallel tomaintain the same Q factor. In other words, the headroom associated withthe single antenna can be applied to parallel antennas while increasingNFC performance for smaller size tags.

Example components of a mobile wireless communications device 1000 thatmay be used in accordance with the above-described embodiments arefurther described below with reference to FIG. 3. The device 1000illustratively includes a housing 1200, a keyboard or keypad 1400 and anoutput device 1600. The output device shown is a display 1600, which maycomprise a full graphic LCD. Other types of output devices mayalternatively be utilized. A processing device 1800 is contained withinthe housing 1200 and is coupled between the keypad 1400 and the display1600. The processing device 1800 controls the operation of the display1600, as well as the overall operation of the mobile device 1000, inresponse to actuation of keys on the keypad 1400.

The housing 1200 may be elongated vertically, or may take on other sizesand shapes (including clamshell housing structures). The keypad mayinclude a mode selection key, or other hardware or software forswitching between text entry and telephony entry.

In addition to the processing device 1800, other parts of the mobiledevice 1000 are shown schematically in FIG. 4. These include acommunications subsystem 1001; a short-range communications subsystem1020; the keypad 1400 and the display 1600, along with otherinput/output devices 1060, 1080, 1100 and 1120; as well as memorydevices 1160, 1180 and various other device subsystems 1201. The mobiledevice 1000 may comprise a two-way RF communications device having dataand, optionally, voice communications capabilities. In addition, themobile device 1000 may have the capability to communicate with othercomputer systems via the Internet.

Operating system software executed by the processing device 1800 isstored in a persistent store, such as the flash memory 1160, but may bestored in other types of memory devices, such as a read only memory(ROM) or similar storage element. In addition, system software, specificdevice applications, or parts thereof, may be temporarily loaded into avolatile store, such as the random access memory (RAM) 1180.Communications signals received by the mobile device may also be storedin the RAM 1180.

The processing device 1800, in addition to its operating systemfunctions, enables execution of software applications 1300A-1300N on thedevice 1000. A predetermined set of applications that control basicdevice operations, such as data and voice communications 1300A and1300B, may be installed on the device 1000 during manufacture. Inaddition, a personal information manager (PIM) application may beinstalled during manufacture. The PIM may be capable of organizing andmanaging data items, such as e-mail, calendar events, voice mails,appointments, and task items. The PIM application may also be capable ofsending and receiving data items via a wireless network 1401. The PIMdata items may be seamlessly integrated, synchronized and updated viathe wireless network 1401 with corresponding data items stored orassociated with a host computer system.

Communication functions, including data and voice communications, areperformed through the communications subsystem 1001, and possiblythrough the short-range communications subsystem. The communicationssubsystem 1001 includes a receiver 1500, a transmitter 1520, and one ormore antennas 1540 and 1560. In addition, the communications subsystem1001 also includes a processing module, such as a digital signalprocessor (DSP) 1580, and local oscillators (LOs) 1601. The specificdesign and implementation of the communications subsystem 1001 isdependent upon the communications network in which the mobile device1000 is intended to operate. For example, a mobile device 1000 mayinclude a communications subsystem 1001 designed to operate with theMobitex™, Data TAC™ or General Packet Radio Service (GPRS) mobile datacommunications networks, and also designed to operate with any of avariety of voice communications networks, such as AMPS, TDMA, CDMA,WCDMA, PCS, GSM, EDGE, etc. Other types of data and voice networks, bothseparate and integrated, may also be utilized with the mobile device1000. The mobile device 1000 may also be compliant with othercommunications standards such as 3GSM, 3GPP, UMTS, 4G, etc.

Network access requirements vary depending upon the type ofcommunication system. For example, in the Mobitex and DataTAC networks,mobile devices are registered on the network using a unique personalidentification number or PIN associated with each device. In GPRSnetworks, however, network access is associated with a subscriber oruser of a device. A GPRS device therefore typically involves use of asubscriber identity module, commonly referred to as a SIM card, in orderto operate on a GPRS network.

When required network registration or activation procedures have beencompleted, the mobile device 1000 may send and receive communicationssignals over the communication network 1401. Signals received from thecommunications network 1401 by the antenna 1540 are routed to thereceiver 1500, which provides for signal amplification, frequency downconversion, filtering, channel selection, etc., and may also provideanalog to digital conversion. Analog-to-digital conversion of thereceived signal allows the DSP 1580 to perform more complexcommunications functions, such as demodulation and decoding. In asimilar manner, signals to be transmitted to the network 1401 areprocessed (e.g. modulated and encoded) by the DSP 1580 and are thenprovided to the transmitter 1520 for digital to analog conversion,frequency up conversion, filtering, amplification and transmission tothe communication network 1401 (or networks) via the antenna 1560.

In addition to processing communications signals, the DSP 1580 providesfor control of the receiver 1500 and the transmitter 1520. For example,gains applied to communications signals in the receiver 1500 andtransmitter 1520 may be adaptively controlled through automatic gaincontrol algorithms implemented in the DSP 1580.

In a data communications mode, a received signal, such as a text messageor web page download, is processed by the communications subsystem 1001and is input to the processing device 1800. The received signal is thenfurther processed by the processing device 1800 for an output to thedisplay 1600, or alternatively to some other auxiliary I/O device 1060.A device may also be used to compose data items, such as e-mailmessages, using the keypad 1400 and/or some other auxiliary I/O device1060, such as a touchpad, a rocker switch, a thumb-wheel, or some othertype of input device. The composed data items may then be transmittedover the communications network 1401 via the communications subsystem1001.

In a voice communications mode, overall operation of the device issubstantially similar to the data communications mode, except thatreceived signals are output to a speaker 1100, and signals fortransmission are generated by a microphone 1120. Alternative voice oraudio I/O subsystems, such as a voice message recording subsystem, mayalso be implemented on the device 1000. In addition, the display 1600may also be utilized in voice communications mode, for example todisplay the identity of a calling party, the duration of a voice call,or other voice call related information.

The short-range communications subsystem enables communication betweenthe mobile device 1000 and other proximate systems or devices, whichneed not necessarily be similar devices. For example, the short-rangecommunications subsystem may include an infrared device and associatedcircuits and components, a Bluetooth™ communications module to providefor communication with similarly-enabled systems and devices, or a nearfield communications (NFC) sensor for communicating with an NFC deviceor NFC tag vian NFC communications.

Many modifications and other embodiments will come to the mind of oneskilled in the art having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it isunderstood that various modifications and embodiments are intended to beincluded within the scope of the appended claims.

That which is claimed is:
 1. A mobile wireless communications devicecomprising: a portable housing; an NFC transceiver carried by saidportable housing; and an antenna assembly carried by said portablehousing and coupled to said NFC transceiver, and comprising a pluralityof nested loop antennas coupled in parallel and progressively increasingin size from an innermost loop antenna to an outermost loop antenna. 2.The mobile wireless communications device of claim 1, wherein saidplurality of nested loop antennas is non-concentric.
 3. The mobilewireless communications device of claim 1, wherein said plurality ofnested loop antennas comprises three loop antennas.
 4. The mobilewireless communications device of claim 1, wherein each loop antenna hasa rectangular shape with opposing ends and opposing sides coupledthereto.
 5. The mobile wireless communications device of claim 4,further comprising a pair of antenna feed points; and wherein saidplurality of nested loop antennas each have respective ends adjacent oneanother, and adjacent said pair of antenna feed points and coupledthereto.
 6. The mobile wireless communications device of claim 1,wherein said antenna assembly further comprises a dielectric substrate,and wherein each loop antenna comprises at least one loop conductorcarried by said dielectric substrate.
 7. The mobile wirelesscommunications device of claim 1, wherein said portable housingcomprises a removable battery cover, and wherein said antenna assemblyis carried by said removable battery cover.
 8. The mobile wirelesscommunications device of claim 1, wherein said innermost loop antenna isabout 15 mm by 15 mm, and wherein said outermost loop antenna is about85 mm by 54 mm.
 9. The mobile wireless communications device of claim 1,further comprising a cellular transceiver carried by said portablehousing, and a cellular antenna coupled to said cellular transceiver.10. A mobile wireless communications device comprising: a portablehousing comprising a removable battery cover; a cellular transceivercarried by said portable housing; a cellular antenna coupled to saidcellular transceiver; an NFC transceiver carried by said portablehousing; and an antenna assembly carried by said removable battery coverand coupled to said NFC transceiver, and comprising a plurality ofnested loop antennas connected in parallel.
 11. The mobile wirelesscommunications device of claim 10, wherein said plurality of nested loopantennas progressively increase in size from an innermost loop antennato an outermost loop antenna.
 12. mobile wireless communications deviceof claim 10, wherein said plurality of nested loop antennas isnon-concentric.
 13. The mobile wireless communications device of claim10, wherein said plurality of nested loop antennas comprises three loopantennas.
 14. The mobile wireless communications device of claim 10,wherein each loop antenna has a rectangular shape with opposing ends andopposing sides coupled thereto.
 15. The mobile wireless communicationsdevice of claim 14, further comprising a pair of antenna feed points;and wherein said plurality of nested loop antennas each have respectiveends adjacent one another, and adjacent said pair of antenna feed pointsand coupled thereto.
 16. The mobile wireless communications device ofclaim 10, wherein said antenna assembly further comprises a dielectricsubstrate, and wherein each loop antenna comprises at least one loopconductor carried by said dielectric substrate.
 17. The mobile wirelesscommunications device of claim 10, wherein said innermost loop antennais about 15 mm by 15 mm, and wherein said outermost loop antenna isabout 85 mm by 54 mm.
 18. A method for making a mobile wirelesscommunications device comprising: positioning an NFC transceiver withina portable housing; and coupling an antenna assembly to the NFCtransceiver within the portable housing, the antenna assembly comprisinga plurality of nested loop antennas connected in parallel andprogressively increasing in size from an innermost loop antenna to anoutermost loop antenna.
 19. The method of claim 18, wherein theplurality of nested loop antennas is non-concentric.
 20. The method ofclaim 18, wherein the plurality of nested loop antennas comprises threeloop antennas.
 21. The method of claim 18, wherein each loop antenna hasa rectangular shape with opposing ends and opposing sides coupledthereto.
 22. The method of claim 21, wherein the mobile wirelesscommunications device comprises a pair of antenna feed points; andwherein the plurality of nested loop antennas each have respective endsadjacent one another, and adjacent the pair of antenna feed points andcoupled thereto.
 23. The method of claim 18, wherein the antennaassembly further comprises a dielectric substrate, and wherein each loopantenna comprises at least one loop conductor carried by the dielectricsubstrate.
 24. The method of claim 18, wherein the portable housingcomprises a removable battery cover, and wherein the antenna assembly iscarried by the removable battery cover.
 25. The method of claim 18,wherein the innermost loop antenna is about 15 mm by 15 mm, and whereinthe outermost loop antenna is about 85 mm by 54 mm.